随机粗糙表面上剪切变稀流体液滴的沉积过程模拟

采用计算流体力学相场方法模拟了单个剪切变稀非牛顿流体液滴在随机粗糙表面的沉积过程，并分析揭示了随机粗糙表面形貌对液滴运动状态及平衡状态的影响。结果表明，在指定的相同操作条件下，即使在光滑表面，剪切变稀流体液滴比牛顿流体液滴铺展更大且回缩至平衡所需时间更少，不存在二次铺展；剪切变稀流体液滴最大铺展直径随均方根粗糙度Rr与Wenzel粗糙度Wr的增加而略有增加。Wr相同时，随着Rr增大，液滴最终铺展系数减小，高度系数增大，平衡接触面积及接触角有所减小。在Rr相同情况下，随着Wr增大，液滴达到平衡所需时间缩短，平衡接触面积线性增大。

Numerical simulation of shear-thinning droplet impacting on randomly rough surfaces

The computational fluid dynamics phase field method was used to simulate the deposition process of single shear thinning non-Newtonian fluid droplets on a random rough surface. The analysis revealed the influence of random rough surface morphology on the movement state and equilibrium state of droplets. It was shown that, even on a smooth surface,under the same operating conditions,a shear-thinning droplet can demonstrate quite different impact behavior as compared with a Newtonian droplet. The shear-thinning property offers a much larger spreading ratio,and shorter time to reach equilibrium. The initial spreading phase is followed by a recoiling to equilibrium phase for the shear-thinning droplet,while the Newtonian droplet has a second spreading phase after the recoiling phase. On randomly rough surfaces,the maximum spreading ratio increases with the increase of either root-mean-square roughness(Rr)or Wenzel roughness parameter(Wr). With the same value of Wr,increasing Rr can lead to the decrease of the final spreading ratio,and slight decreases of equilibrium contact area and contact angle. With the same value of Rr,increasing Wr offers a faster deposition to reach an equilibrium state,and a linearly increased contact area.